Brake Pressure Problem.

[supersnake83]

Hi Everyone,

From my previous posts about a brake master cylinder problem, I took your advice and changed my master cylinder and bleeded the whole system. However, my problem with my brake pressure being low is still the same.

Here is the symptom. When I am driving, sometimes (actually, all of the time) I have to put the brake pedal to the floor to stop the car. I do have quite new brakes shoes on the car with only about 10% wear.

The service manual noted how to check the brake booster pressure, which is to run the car for a few minutes, depress the pedal a few times, cut the engine off, and pump the brakes. If the brake pedal gets tight after the first pump, then the brake booster is fine (which mine is fine).

Now I am at a standstill. All of the brakes have been bleeded in the correct order (rr, lr, rf, lf) and a new master cylinder has been put on. All of the hoses and lines have been checked and no cracks or leaks exist.

If anyone have any suggestions about what to check or change, or what else I can troubleshoot, please let me know.

Thanks all,

Geoff.
Modified by supersnake83 at 1:40 PM 6/10/2007

[supersnake83]

Just some more info.

If anyone can help.

Usually when I depress the brake pedal the first time is when it is really low, but when I depress it a second time immediately after the first when coming to a stop, the pedal's pressure do increase.

Also, I have noticed that I can hear my brake pedal pushing air. I don't know if this is normal, but just something I have noticed. I did notice this before I changed to master cylinder.

Hope someone can help.

Thanks,

Geoff.

[yodawill2000]

Sure seems like theres air in the system.Weird for sure.

[gr8scott72]

Sure seems like theres air in the system.Weird for sure.

I agree. Who bled (past tense is bled, not bleeded) your brakes? If it was you, how did you do it?

[supersnake83]

My brother and I bled (thanks for the correction) the brakes after we bench bled the master cylinder.

Here was the bleeding precedure.

I pumped the brakes a few times (acutally, it was like 20 times each time), then my brother opened the bleeder screw while I held the pedal to the floor.

We did this like 5 times for each wheel. That was to make sure that there was a constant flow of fluid.

All of this was done while the car was off.

Thanks,

Geoff.

P.s.

If it sounds like we did something wrong, please let me know. Also let me know if we should re-bleed the brakes.

[gr8scott72]

Did he cap off the bleeder valve (tighten) before you let off the brake pedal?

[supersnake83]

Yes.

I held my foot on the pedal, he opened the bleeder valve, drained the fluid and tightened it before I started pumping again.

I will probably buy another quart of fluid and re-bleed the whole system probably on Tuesday just to be on the safe side knowing it is not air in the system.

But if there is anything else I should check, then please, by all means let me know.

Thanks,

Geoff.

[driverdriver]

Are your calipers closing correctly? Have you observed?

[supersnake83]

Please, elaborate a little more. I will have my dad help me this time when I re-bleed my brakes.

Let me know what we should be looking for.

Thanks,

Geoff.

[supersnake83]

O.k.

Here are some more results. I did check the calipers and all four of them are working fine. What I did to test them was: while the caliper was off, I had my friend pump the brakes to see if the caliper was moving to tighten and then loosen a little bit.

I did that over 10 times with each caliper letting it tighten on a wood block that I had while the car was running.

There are some things that I found that could be a problem. The front two calipers, the top pistons were rusted on the inside. They still worked, but when I used my c-clamp to push the pistons back, the bottom piston came out first, then the top; but when both were out fully on the wood, they appeared to be appying the same pressure; but I only had my friend press the pedals, about 10 or 12 times.

The other thing is that sometimes when I am moving my car from my driveway, to let people out, I sometimes feel/hear that the pedal or caliper is getting stuck on something when I push the brake pedal. It will only last about a second, and then it will go away. Afterwards, I won't feel it.

Another thing is on the front, the brake pads on both sides (left and right) and on both sides of the rotor are not wearing evenly. On each of the front wheels, the inside pad is worn more at the bottom and less at the top, on the outside it is the opposite. (same for both wheels). The back, there is little to no wear on the set of pads on each wheel. (I don't know if this is normal or not).

I don't know what else to check.

If anyone else has any ideas, please let me know.

Thanks for all the help so far,

Geoff.

[supersnake83]

Hi again everyone.

Is it possible that something with the ABS system could have something to do with my brake pressure problem?

My ABS light does come on every now and then, but I just tap the relay box in the engine compartment and the light and ABS motor stops whining loud like it does when the light comes on.

Just another thought.

Thanks,

Geoff.

[supersnake83]

Is it possible that there could be a problem with the brake pressure regulator/sensor or whatever the device is that controls brake pressure?

Thanks anyone/everyone,

Geoff.

[NismoChi]

Did you bleed the new master cylinder good before you put it in?

[supersnake83]

My brother and I bench bled the master cylinder until there was a steady flow of fluid coming out of the tubes. We then bled the brakes in the following order, rr, lr, rf, lf.

I am suspecting that the problem is one of three things:

1. One or both of my front calipers need to be replaced; both have a rusted top piston and I often feel vibration when I press the brake peddal, although my front suspension is fine.

2. I purchased a bad rebuilt Cardone brake master cylinder.

3. My problem could be a brake pressure sensor, relay, pump or something. I do know that the FSM has a picture of what I think controls the brake pressure. I will look it up and post a reply as to what page.

I will still try and investigate, but my time is running short; my brakes are litterally touching the floor when I depress the pedal for the first time, but when I depress it a second time, I get a little more tightness/pressure. I do know that the original master cylinder on my car did not leak and thus I beleive that it was fine, so my problem could be elsewhere.

If anyone else could help, thanks,

Geoff.

[NismoChi]

I would put money one #2 to be the problem. It happen to me many times before, bad "new" parts.Not #1, it is normal to have rust on the top piston because the top piston is not touching the back of the pad at any time. also the vibration you got from the brake is most like from the rotors.

Don't know much about #3, have nothing to say on that.

[fatselectronics]

did you check the brake fluid the same thing happened in my nissan leopard and i was out of fluid filled up and was good to go just a though sure you tried it already though. By the way my ABS is always on too not sure why and i donot know which relay it is since they all in japanesse (Sucks)

[supersnake83]

Hi again eveyone.

I just received my new OEM master cylinder and the mechanic put it on and my problem is still there. I still have to put the pedal to the floor before the car starts to slow down. Only after I pump the brakes once or twice more, will my pressure increase to make my car stop.

Is there anyone that may have had a similar problem like this? and if so, what was your solution.

Please help and again, thanks for any help,

Geoffrey.

[supersnake83]

Great news everyone.

The mechanic I took my car to this time was able to solve my problem. It is still not clear if the rebuilt or my original master cylinder was bad, but since I have a brand new OEM, I won't complain (except for the extra $250.00 I shelled out for this part and $150.00 for labor--I'll explain below).

Hopefully this entire thread can help someone else in the future if they have the same problem.

The mechanic solved my problem by doing a full system bleed which he said is not usual to have to do this. Since our cars (J30) have an ABS system, he said that after you bleed the brake system from the calipers, the ABS system has to be bled also.

I didn't know this.

He said that the order of bleeding is the master cylinder, the brakes (rear to front) and then the ABS system has to also be bled as well. He said he had to hook my ABS device to a machine that pumped the system. He said this is called a "reverse flush" or something to that effect.

I was charged 97.50 orginally for labor, but factoring in the extra time/labor into bleeding the ABS system, I was charged 35.00 more; fluid, and tax, brought my total to 150.00 even.

I am glad that I now have brake pressure and thank you to everyone for your input/help.

Geoffrey.
Modified by supersnake83 at 6:20 PM 9/28/2007

[gr8scott72]

Great news everyone.

The mechanic I took my car to this time was able to solve my problem. It is still not clear if the rebuilt or my original master cylinder was bad, but since I have a brand new OEM, I won't complain (except for the extra $250.00 I shelled out for this part and $150.00 for labor--I'll explain below).

Hopefully this entire thread can help someone else in the future if they have the same problem.

The mechanic solved my problem by doing a full system bleed which he said is not usual to have to do this. Since our cars (J30) have an ABS system, he said that after you bleed the brake system from the calipers, the ABS system has to be bled also.

I didn't know this.

He said that the order of bleeding is the master cylinder, the brakes (rear to front) and then the ABS system has to also be bled as well. He said he had to hook my ABS device to a machine that pumped the system. He said this is called a "reverse flush" or something to that effect.

I was charged 97.50 orginally for labor, but factoring in the extra time/labor into bleeding the ABS system, I was charged 35.00 more; fluid, and tax, brought my total to 150.00 even.

I am glad that I now have brake pressure and thank you to everyone for your input/help.

Geoffrey.

Modified by supersnake83 at 6:20 PM 9/28/2007

I'm glad you finally got it fixed.